Creating a new small tunnel into the Pike River Mine drift is one of three re-entry scenarios which have been investigated by technical experts in Greymouth over the past two days.
The Pike River Recovery Agency was set up by the Government earlier this year to plan the safe, manned re-entry and recovery of the drift access tunnel, to try and find out what happened in order to prevent any further tragedies of this nature; to give the families closure; and where possible, retrieve any remains found in the drift.
Seven Agency-contracted technical experts, Family Reference Group representatives and two of their expert advisors, Agency staff, the Minister’s Independent Advisor Rob Fyfe, and representatives from the Department of Conservation, Worksafe and New Zealand Mines Rescue this week focused on ventilation and geotechnical engineering for the re-entry concept plan.
The three scenarios which are now being developed further include building a new two metre by two metre tunnel, around 200 metres long, to the Pit Bottom in Stone area; drilling a large diameter borehole; and re-entering the main drift as it is with no second means of egress (exit).
“A 2metre by 2metre tunnel, if it can be achieved, would provide ventilation, a second means of egress and quicker access to the areas of interest to assist with finding out what happened and recovering any remains,” Agency Chief Executive Dave Gawn says.
“There are other options as well, including the drilling of a new large diameter borehole which would assist ventilation and possibly act as a means of escape. At this stage no final decisions have been made.
“The input of ventilation and engineering experts, with the detailed chemistry and geological engineering knowledge in the room, combined with hundreds of years of mining experience, has enabled us to get closer to finalising a preferred option,” Mr Gawn says.
A concept plan drafted following an earlier four day workshop has been sent to the Minister Responsible for Pike River Re-entry Andrew Little. Minister Little will make a decision based on the advice in the concept plan about whether the Agency should proceed to the next stages.
Family Reference Group representatives Bernie Monk and Anna Osborne remained enthused about the concept plan and the work being done to refine it.
“These guys are working from a position that we will be re-entering, and a lot of this is standard mining practice around the world. It’s been fascinating and positive to hear the details of how they’re planning to expel the methane, introduce the nitrogen and then bring in fresh air,” Anna says.
Mr Gawn says preferred supplier(s) carrying out any approved work will also be involved in detailed recovery planning and risk analysis, as well as mine sealing and rehabilitation works at the completion of the project. A procurement process is underway to find the right contractor for that work.
“We need to continue our planning even while the Minister is making his decision about whether he’s confident that re-entry is possible. The Pike River families have been waiting for more than seven years now and it’s important that we keep the pace up, while not sacrificing any finer details around health and safety,” Mr Gawn says.